In the building composite industry, various methods have been developed in an attempt to improve the mat strength and stability of non-woven fiberous mats. Many efforts are focused on modifying the binder systems. The following patents and publications are representative of such endeavors:
U.S. Pat. No. 4,335,186 discloses a chemically modified asphalt composition where the asphalt is reacted with a nitrogen-containing organic compound which is capable of introducing to the asphalt functional groups that can serve as reactive sites to establish a secure chemical bond between the asphalt and reinforcing fillers, blended into the asphalt, such as glass fibers and siliceous aggregates.
U.S. Pat. No. 4,430,465 relates to an article of manufacturing comprising mat fibers, such as glass fibers, that are coated with a composition comprising asphalt, an alkadiene-vinylarene copolymer, a petroleum hydrocarbon resin and a branched organic amine which is employed as an anti-stripping agent.
U.S. Pat. No. 5,518,586 provides a method of making a glass fiber mat comprising dispersing glass fibers in an aqueous medium containing hydroxyethyl cellulose to form a slurry; passing the slurry through a mat forming a screen to form a wet fiber glass mat; applying a binder comprising a urea-formaldehyde resin, a water-insoluble anionic phosphate ester and a fatty alcohol to the wet glass fiber mat; and curing the binder.
U.S. Pat. No. 5,744,229 discloses a glass fiber mat made with a polymer-reacted asphalt binder. The disclosed binder of the glass fiber mat includes an aqueous emulsion of a polymer modified asphalt produced by the reaction of asphalt, a surfactant, and a phenol-, resorcinol-, urea- or melamine-formaldehyde resin.
U.S. Pat. No. 4,500,600 describes glass fibers coated with a size composition comprising γ-aminopropyltriethoxysilane and an alkoxysilane.
In addition to modifying the binder systems, some efforts have focused on increasing the mat strength through the use of fibers having different lengths. For example, U.S. Pat. No. 4,472,243 provides a sheet type felt material and sheet type roofing material such as shingles and rolls made therefrom. The felt comprises 10-60 weight % glass fibers having varying lengths, 15-80 weight % cellulose fiber and 5-25 weight % binder. The binder include acrylamides, starch, urea resins, phenol resins, sodium silicates, epoxy resins, styrene-butadiene rubber, acrylic, neoprene, and acrylonitrile.
U.S. Pat. No. 5,585,432 discloses reinforced polymer composites having a uniform mixture of reinforcing fibers having a polymordal length distribution and having polymer particles distributed therein. Fillers such as silicon dioxide, calcium carbonate, magnesium oxide, CaSiO3 and mica may also be present in the polymer composite.
Although improved mat strength may be accomplished using fibers of different lengths, this improved strength typically does not hold when a shingle is formed by coating the mat with asphalt. In view of the above drawbacks with the prior art, there is still a continued need to provide a new and improved non-woven mat which has improved tear strength even after it is coated with asphalt.